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Lots of politicians have 20:20 hindsight. Foresight, however, is generally in shorter supply, which explains why Vince Cable is being acclaimed once again, tipped at the age of 69 both as a potential successor to either the 40-something George Osborne as Chancellor and/or the 40-something Nick Clegg as Lib Dem leader. The ‘Septuagenarian Sage of Twickenham’ is enjoying a Second Coming-of-age. Age does not weary him, nor the years condemn. What’s his secret?

Principally, it’s Vince’s tendency to be validated by subsequent events. For years he was a lonely voice worrying away at the ever-increasing spiral of private debt while the rest of the political class blithely ignored his warnings… until The Storm hit the economy in 2007, and he was canonised for his prophesy.

Then his halo slipped. Within the space of a couple of months he not only junked the Lib Dems’ long-standing pledge to abolish tuition fees, but also almost got himself sacked for indiscreetly claiming to an undercover journalist that he had ‘declared war’ on the Murdochs.

As a result, a key part of his departmental brief, media regulation, was promptly handed to Jeremy Hunt (ah, hindsight!), and Vince was consigned to the graceless status of fallen saint.

But now his resurrection is (almost) complete. Yesterday’s Daily Mirror front page – not a place Lib Dems are used to being praised – demands “it’s time for Plan V (that’s kick out useless Osborne and bring in Vince Cable”. And his casual remark to the Financial Times in an interview that he “wouldn’t exclude” the possibility of running for the party leadership in the event of a vacancy has fuelled speculation about his broader ambitions.

Vince is no political ingénue. He will have been aware how answering such a hypothetical question would be hyped-up by the media. And a part of him will relish it: Vince, like all successful politicians, has an ego. For all his twinkling geniality and measured modesty in interviews, this is a man who likes the limelight: he’s waltzed with Alesha Dixon on Strictly Come Dancing and joshed with Ian Hislop on Have I Got News For You.

Vince Cable is destined to earn the title “the best Chancellor we never had”. I don’t believe for one moment that David Cameron will dare move George Osborne from the Treasury in the coming reshuffle.

But if he does it won’t be Vince who moves into Number 11: the angsty Tory backbenches won’t tolerate a Lib Dem driving the Coalition’s economic policy.

Bizarrely more plausible is the scenario in which Vince succeeds Nick Clegg… It’s 2014, Nick Clegg’s approval ratings are still flagging; the opportunity to become an EU commissioner proves just too tempting; and Vince steps in to care-take the Lib Dems into the trickiest election the party will have faced since 1979. Vince will have the credibility as a cabinet minister to be able to defend the party’s role in Coalition; yet his evident semi-detachment may woo back those disaffected former Lib Dem voters worried the party’s been swallowed-up by the Tories.

Would he be a successful Lib Dem leader? I’m unconvinced. Though he has that rare ability to speak to the full spectrum of Lib Dems – an Orange Book liberal who prefers the label ‘social democrat’ – he has a habit of springing surprise announcements on the party, from his hasty welcome of the Browne Report’s fee-hiking recommendations to his proposal for a ‘mansion tax’ launched without any consultation at the party’s 2009 conference. It’s the kind of behaviour more forgiven if you’re not leader.

On the balance of probabilities, I still think Leader Vince an unlikely outcome. But it cannot be ruled-out entirely. If it came to pass, it would be (among other things) a massive irony, for it is Nick Clegg’s breaking of the Lib Dems’ tuition fees pledge which remains – as Iraq was for Tony Blair – the issue that continues to define him for much of the public. Yet who was the architect of that policy U-turn? It’s that man Vince again.